<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>盒子模型</title>
    <style>
        *{
            margin: 0px;
            padding: 0px;
        }
        div{
            width: 300px;
            height: 200px;
            background: red;
            /*边框*/
            border: 5px solid greenyellow;
            /*内边距*/
            padding: 10px 8px 5px 100px;
            /*外边距*/
            margin: 20px;
        }
    </style>
</head>
<body>
    <div>我是一个盒子</div>
</body>
</html>